Method of forming metallic tips



July 13, 1937. c. PFANSTIEHL METHOD OF FORMING METALLIC TIPS 2 Sheets-Sheet l Filed Jan. 15, 1936 y 1 7- c. PFANSTIEHL METHOD OF FORMIN METALLIC TIPS 2 SheetsSheet 2 Filed Jan. 15, 1956 Patented July 13, 1937 UNITED STATES PATENT OFFICE METHOD OF FORMING METALLIC TIPS Carl Pfanstiehl, Highland Park, Ill., assig'nor to Pfanstiehl Chemical Company, a corporation of Illinois Application January 15, 1936, Serial No. 59,299

4 Claims. (01. 115-32) This invention relates to forming metallic tips, a high temperature after substantially all of the and more particularly to a method of tipping mecarbon dioxide has been expelled therefrom. tallic bases, such as pen points and other like Such a crucible is particularly suitable for use articles. with very high melt point metals, and especially 5 In my U. S. Patent No. 2,005,752, issued June 25, such as are described in my co-pending applica- 1935, there is described a method of tipping metion, Serial No. 753,220, filed November 15, 1934. tallic bases in which the tip is first tacked to the Any siifii ien ly r r ctory ru i l which th metallic article and is then welded byheat supmetal does not wet may be employed, however. plied substantially entirely through the, tip. Diam ri lly pp posts 8 and I9 r In my co-pending application, Serial No. 36,- provided within the tube 50 and are imbedded 229, filed August 14, 1935, now Patent 2,032,887, in the base I and connected to a circuit, as issued March 3, 1936, is described a method of S ow in Fi ents 0 and 2 are Set in welding tips to metallic bases without prelimithe posts at a height just below the cup I6 and the narily tacking them in place, .but in which the crucible l 5 tip and base are held in lightly pressed contact A D nib er p ded w l s 23 while welding. and adapted to hold a pen nib 24, seats itself on In the case of certain materials it has now been the spring 25 a short distance above the crucible found advantageous to form a tip upon a base H. In normal operations it has been found satby fusing a small portion of tip material upon a isfactory to maintain the pen nib about inch 50 medium which it does not wet, the amount of above the crucible. In operation, sufiicient metal material being small enough that it will spheroid to form a tip of the desired size is measured and itself by surface tension upon fusion, and then dropped into the crucible, either in powdered dipping the base into the formed spheroid, which form or otherwise, as indicated at 26 in Fig. 2. has the effect of freezing the spheroid and firmly The electric circuit may then be turned on and welding it to the base. maintained until the metal has completely fused H This method is particularly applicable to the and formed a spheroid of molten metal. In the welding of high melt point materials such as case of alloys described in my application, Serial iridium upon relatively low melt point bases such No. 753,220, it is advantageous to maintain the as steel. pellet molten for some time.

The invention is illustrated diagrammatically In many instances, it is found preferable to in the drawings, in which-- maintain the current continuously, simply drop- Fig. 1 is an elevation, partly in section and ping in measured amounts of metal from time partly broken away, of the welding apparatus; to time. Fig. 2 is a sectional elevation, much enlarged, of When the metal has fused sufficiently, the 35 the crucible and p Fig. 3 is a similar secholder 22 is pressed down until the cross piece 21 tional elevation of a modified heating element engages the annulus 28 on the top l2. At this and crucible; Fig. 4 is a similar view of a further point the pen nib will dip into the fused spheroid modification; and Fig. 5 is a diagrammatic wir- 29 and will instantaneously freeze it thereon. ing P for the Welding appa at s Shown in While it is obvious that the pen nib cannot be m Fig. 1. kept in this position long without its fusing, par- AS ust at d in the Welding apparatus ticularly where it is of a lower melt point metal prises a Pyrex tube llv est in a refractory than the tip, the time interval is not critical, and base for example Qf bakelite or Alberene even an inexperienced operator has no difliculty stone' and substantially closed at the top by a in withdrawing the nib with the tip attached be- 15 gg Q ffm P fore refusion occurs. For most metals it is pre- 6 ase 1s provlded wlth passageway ferred that a stream of hydrogen or other inert connected to a source of h dro en, thr u h which hydrogen may be $1 adfnitted gas be passed through the tube l0 constantly to tube ID. A ceramic post I4 is centrally posiavoid oxidation tioned in the base within the tube It! and a In 3 modified tungsten rod is r tungsten, or other refractory metal, post I5 is im- Vided which is Set Within a Ceramic tube D beclded therein. Upon the post is firmly set a vided with a ceramic cap 3i. In this instance molybdenum or tungsten cup washer l6 holding the crucible lla surmounts the tungsten rod and a ceramic crucible ll. This crucible is preferably is Small r than th diam t f t rod beneath 5 of a heat-treated lime which has been heated at it. A tungsten heating coil 32 is provided within the tube and heats the rod sufficiently to melt material within the crucible.

In Fig. 4 a further modification of the heating element is provided, in this instance a tungsten rod being omitted and a ceramic post 33 being provided, surmounted by a tungsten washer 34 within which the crucible is imbedded. A ceramic tube 30b surrounds the post and outside of it a high frequency heating element 35 is provided which may be water cooled if desired. The high frequency element induces a high temperature in the tungsten washer and thereby generates the necessary heat for fusion of material within the crucible.

In the modifications shown in Figs. 3 and 4 it is generally preferable to introduce hydrogen within the ceramic tube.

Fig. 5 indicates a wiring diagram for the heating element shown in Fig. 1, 36 indicating a high voltage transformer, 31 a time switch and 38 and 39 are low voltage transformers leading to a current supply. In operation of the device, an arc is formed between the filaments 20 and 2| which are heated continuously by the low voltage current supply to ionize hydrogen within the tube Ill. The ionized hydrogen permits the formation of the are at substantially its maintenance voltage, this voltage being supplied from the high voltage transformers 36.

The invention is particularly applicable to 10W melt point bases to which are to be attached rela tively high melt point tips. For example, it has been found highly satisfactory in the attaching of iridium or other high melt point tips to steel or stainless steel nibs.

While the invention has been described particularly in connection with pen nibs, it is applicable to other bases and tips, for example, spark plugs, meter pivots and like articles. With meter pivot staffs it is customary to use a. stainless steel 0.050 inch in diameter by one-half inch long which is to be tipped with a hard metal.

The foregoing detailed description has been given for clearness of understanding only, and no unnecessary limitations should be understood therefrom, but the appended claims should be construed as broadly as permissible, in view of the prior art.

I claim:

1. The method of forming ball-shaped tips upon metallic bases, which comprises fusing a predetermined quantity of tip metal, the amount being small enough to spheroid itself by surface tension upon fusion, the fusion being carried out upon a surface not wet by the fused metal, whereby a molten spheroid of tip metal is produced, and contacting the base with the spheroid, whereby the spheroid is chilled and welded to the base, thereby forming a ball-shaped tip of predetermined size.

2. The method as set forth in claim 1, in which the base has a thickness of the order of that of a pen nib.

3. The method as set forth in claim 1, in which the tip has a relatively high melting point compared with the base.

4. The method as set forth in claim 1, in which the base is steel and the tip metal has a melting point of the orderof that of iridium.

CARL PFANSTIEHL. 

